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227 Cards in this Set

consists of a strand of alternating sugars (deoxyribose) and phosphate groups with a nitrogenous base attached to each sugar. The bases are adenine, thymine, cytosine & guanine. DNA exists in a cell as two strands twisted together to form a double helix. The two strands are held together by hydrogen bonds between their nitrogenous bases. The bases are paired in a specific, C-G. The information held in the sequence of nucleotides in DNA is the basis for synthesis of RNA and proteins in a cell.

Bacteria can acquire antibiotic resistance by all of the following except

snRNP's

Suppose you inoculate three flasks of minimal salts broth with E. coli. Flask A contains glucose. Flask B contains glucose and lactose. Flask C contains lactose. After a few hours of incubation, you test the flasks for the presence of B-galactosidase. Which flask(s) do you predict will have this enzyme?

C

Plamids differ from transponsons because plasmids

are self-replicated outside the chromosomes

Mechanism by which the presence of glucose inhibits the lac operon

catabolite repression

The mechanism by which lactose controls the lac operon

induction

Two daughter cells are most likely to inherit which one of the following from the parent cell

a change in a nucleotide in DNA

Which of the following is not a method of horizontal gene transfer

binary fission

Genetics

the study of what genes are, how they carry information, how their information is expressed, and how they are replicated and passed to subsequent generations or other organisms

DNA in cells exists as double-stranded helix; held together by

hydrogen bods between specific nitrogenous base pairs: AT & CG

A Gene

is a segment of DNA, a sequence of nucleotides, that codes for a functional product, usually a protein

The DNA in a cell is duplicated before

the cell divides, so each daughter cell receives the same genetic information

Genotype

is the genetic composition of an organism, its entire complement of DNA

Phenotype

is the expression of the genes; the proteins of the cell and the properties they confer on the organism

The DNA in a chromosome exists as

one long double helix associated with various proteins that regulate genetic activity

Bacterial DNA is

circular
the chromosome of E. coli, for example, contains about 4 million base pairs and is approximately 1000 timex longer than the cell

Genomics

is the molecular characterization of genomes

Information contained in the DNA is transcribed into

RNA and translated into proteins

During DNA replication

the two strands of the double helix separate at the replication fork, and each strand is used as a template by DNA ploymerases to synthesize two new strands of DNA according to the rules of nitrogenous base pairing

The result of DNA replication is two new strands of DNA, each having

a base sequence complementary to one of the original strands.

Because each double-stranded DNA molecule contains

one original and one new strand, the replication process is called semiconservative.

DNA is synthesized in one direction designated 5'--3'. At the replication fork,

the leading strand is synthesized continuously and the lagging strand discontinuously

DNA ploymerase proofreads new molecules of DNA and

removes mismatched bases before continuing DNA synthesis

Each daughter bacterium receives a chromosome that is

virtually identical to the parent's

During transcription, the enzyme RNA polymerase synthesizes

a strand of RNA from one strand of double-stranded DNA, which serves as a template

RNA is synthesized from

nucleotides containing the bases A, C, G, and U, which pair with the bases of the DNA strand being transcribed

RNA polymerase binds the promoter; transcription begins at AUG; the region of DNA that is end point of transcription is the

terminator; RNA is synthesized in the 5'--3' direction

Translation

is the process in which the information in the nucleotide base sequence of mRNA is used to dictate the amino acid sequence of a protein

the mRNA associates with ribosomes, which consists of

rRNA and protein

Three-base segments of mRNA that specify amino acids are called

codons

the genetic code refers to

the relationship among the nucleotide base sequence of DNA, the corresponding codons of mRNA, and the amino acids for which the codons code.

the gentic code is

degenerate; that is, most amino acids are coded for by more than one codon.

of the 64 codons, 61 are sense condons (which code for amino acids), and

3 are nonsense codons (which do not code for amino acids and are stop signals for translation).

the start codon

AUG, codes for methionine

specific amino acids are attached to

molecules of tRNA. Another portion of the tRNA has a base triplet called an anticodon

the base pairing of codon and anticodon at the ribosome results in

specific amino acids being brought to the site of protein synthesis

the ribosome moves along the mRNA strand, as amino acids are joined to form

a growing polypeptide; mRNA is read in the 5'--3' direction

Translation ends when

the ribosome reaches a stop codon on the mRNA.

Regulating protein synthesis at the gene level is energy-efficient because

proteins are synthesized only as they are needed.

Constitutive enzymes

produce products at a fixed rate. Examples are genes for the enzymes in glycolysis.

For these gene regulatory mechanisms, the control is

aimed at mRNA synthesis

Repression

controls the synthesis of one or several (repressible) enzymes

When cells are exposed to a particular end-product,

the synthesis of enzymes related to that product decreases.

In the presence of certain chemicals (inducers),

cells synthesize more enzymes. This process is called induction.

An example of induction

is the production of B-galactosidase by E. coli in the presence of lactose; lactose can then be metabolized.

The formation of enzymes is determined by

structural genes.

In bacteria, a group of coordinately regulate structural genes with related metabolic functions, plus

the promoter and operator sites that control their transcription, are called an operon.

In the operon model for an inducible system, a regulatory gene codes for

the repressor protein.

When the inducer is absent, the repressor binds to the

operator, and no mRNA is synthesized.

When the inducer is present, it bind to the

repressor so that it cannot bind to the operator; thus, mRNA is made, and enzyme synthesis is induced.

In repressible systems, the repressor requires

a corepressor in order to bind to the operator site; thus, the corepressor controls enzyme synthesis.

Transcription of structural genes for catabolic enzymes (such as B-galactosidase) is induced by the absence of

glucose. Cyclic AMP and CRP must bind to a promoter in the presence of an alternative carbohydrate.

The presence of glucose inhibits

the metabolism of alternative carbon sources by catabolite repression.

A mutation

is a change in the nitrogenous base sequence of DNA; that change causes a change in the product coded for by the mutated gene.